This invention is related to electro-mechanical modulators and particularly to a modulator for a radiant energy source. The general purpose of the invention is to provide a modulator for such radiant energy sources as lasers, infrared, ultraviolet, white light, etc., and having all of the advantages and none of the disadvantages of presently available choppers and modulators. The instant invention also provides a working tool for electronic laboratories doing research in the fields of lasers, ultraviolet and infrared radiation, etc.
There are presently many types of electro-mechanical modulators and choppers in the prior art. All these choppers ordinarily use vanes or rotary devices to chop a source of energy. These prior type choppers and rotary devices have a number of limitations which are overcome by the present invention.
Several choppers use a tuning fork principle to do the chopping. The tuning fork is usually excited by an electro-mechanical device such as a solenoid and maintained at its resonant frequency by keeping current flowing through the solenoid.
A limitation to these devices is the inability to change their rates of vibration (frequency), requiring the whole mechanism to be changed to change frequency. The size and frequency rates are greatly limited. There are very few tuning fork choppers that can chop lower than 10 hertz per second.
Rotary type choppers use wheels with notches cut in them for chopping the source, usually a motor and a motor controlling device is used in these to drive the chopper wheels. To change the frequency of a rotary chopper, either the speed of the motor, the wheel, or the number of notches in the wheel must be changed. All such changes consume valuable time when making multiple tests.
In both the rotary type of chopper and the tuning device type of chopper involving the fluttering vane type, there is a great deal of mass that has to be overcome, and a frequency change is a relatively slow process.
There are solid state, crystal type choppers or socalled modulators. In most cases, the crystal type chopper has to be resonated at the natural resonance of the crystal, usually above 100 Kc; therefore, placing a limitation on these type devices as far as the lower frequencies are concerned. If lower frequencies are desired, associated complex electronics circuitry is required with the device which often necessitates repairs and calibrations.